Production of alkali sulphates



Patented Feb. 24, 1931 FFICE THEODOR THORSSELL AND AUGUST KRISTENSSON, KASSEL, GERMANY PRODUCTION OF ALKALISULPHATES No Drawing. Application filed May 3, 1929, Serial No. 360,318, and in Germany May 7, 1928.

According to our prior application Serial No. 319,006, filed November 19., 1928, potassium sulphate is prepared by the conversion of potassium chloride with magnesium sul-' phate in an ammoniacal solution of ammonium chloride. 1

lVith the help of this process a suitable crude potash salt can be worked up very advantageously according to the present invention, in such a way, that all its constituents are obtained in refined products Which are commercially pure.

Suitable crude salts for this process are those sylvinitic salts, which in addition to potassium chloride and sodium chloride contain chiefly kieserite.

In order to carry out the process, the composition of the crude salt must first of all be so adjusted that the ratio between potassium chloride and kieserite is approximately the right one. This can either be done by mixing different batches of salt from the mine or by adding potassium chloride or the mixture of kieserite and sodium chloride obtained in the manufacture of potassium chloride and which has hitherto been discarded.

Since kieserite-as is knoWnis not reactive in itself, it is first hydrated to magnesium sulphate. In order to facilitate this hydration, the crude salt is preferably roasted or finely ground prior to being used for manufacture. The crude salt prepared in this way is heated with mother liquor from 95 a preceding operation which is as free from ammonia as possible or poor in ammonia, in which case the said hydration of the kieserite takes place readily. The mother liquor must be as free from ammonia as possible, because 49 ammonia hinders hydration. WVhen the latter is ended, the mixture is cooled and ammonia introduced, in which case the heat of solution of the ammonia must be eliminated by cooling, so that the temperature remains 157 practically constant.

Vhen the reaction is complete the substance in regard to amount of ammonia and temperaing ammonium carbonate, the sodium of the ture the content of sodium sulphate is sub stant1a1ly less than in glaserite nnsorsmsoo. V

The settled substance is separated and stirred oxide, the magnesia is precipitated as o5 .neslum ammonium carbonate. This precipitation of magnesia takes place practically quantitatively, so that the liquor then'conta-ins ammonium carbonate, sodium chloride and a larger quantity of ammonium chloride. The magnesium ammonium carbonate is a good initial material for the preparation of other magnesium compounds, in which case ainmonia and carbon dioxide are recovered for the process.

When magnesium ammonium carbonate is dried, ammonia, carbon dioxide and water of crystallization are given off, and magnesium carbonate is obtained. If heated to a further extent, a further amount of carbon dioxide is given'off, so that finally magnesium oxide remains behind. Magnesium ammonium car bonate or magnesium carbonate heated with ammonium chloride, supply anhydrous magnesium chloride whereas ammonia and carbon dioxide are recovered for the process.

The magnesium ammonium carbonate mother liquor is cooled, as a result of which the majority of its ammonium chloride is precipitated. If magnesium ammonium carbonate is not taken out separately beforethis cooling, the above-mentioned mixture of ammonium chloride and magnesium ammonium carbonate is obtained which afterdrying and calcination gives anhydrous magnesium chloride, returning carbon dioxide and ammonia for the process.

By introducing carbon dioxide into the ammonium chloride mother liquor containgol.

sodium chloride contained therein, is precipitated and separated as sodium bicarhonate.

The bicarbonate mother liquor contains salt chiefly containing kieserite, While the other contents of the crude salt are obtained as commercial products, so that M is obtained from MgCO Na from M1 and mainly ammonium chloride with ammonium Cl in the form of NH cl. lJlCtll'bOlliltG and sodium chlor de. It is heat- The mother liquor obtained at the terminaedior the purpose of removing carbon (11- t on of the process. consists, of an NH,,C1 soluoxide and ammonia and used for the treattion, and when such a. solution is to be used ment of the crude salt mentioned at the outduring a crude salt treatment in the beginset, the process being thus made into a conning of the process, this invention describes tmuous cycle process. the use of the, said mother liquor. for this In conclusion it is emphasized that the purpose. In th s manner a closed ring procpresent 1nvent1on being a further developess is created, Winch is exceedingly important ment of the above. mentioned OOPQIlCllllgttT): tor the manufacture on .a large scales plication uses the basic idea whereby K A diagrammatlc example of this method 80 18 produced directly from a sylvinitic potash follows:

Example H20 K Na NH4 M); H Cl 80.1 CO OE Main-process 7 Initial liquor The liquoris heated with 1000 kg. crude sal kg. MgSO4+aq. 3,60 kg..NaCl

There are introduced at 40 400 kg. NH3+318 Precipitated 596 kg. glaserito-f-KOl are separated 300 kg. NEH-318 kg. H20 are drawn oil A mixture of 200 kg. NH3+380 kg. OOH-212 troduced Precipitated salt 540 kg. MgLNHOdCOQZ-H aq. is sep Med 560 kg. NH4C-l are precipitated by cooling mother liquor Precipitated salt 517 kg. NQHCO: is separated 142 6-2 369 n The liquor is heated for the purpose of inspissating and removing NHr and C0 148 kg. NR3, 380kg. GO and 617 kg. 1190 are I removed l 460 157 8-7 519 Conversion H+OH=H20 +423 23 6 'lh'e liquor together with the sulphate mother liquor is used as initial-liquor: 2400 l 104. 07 229 002 44 flla'nufacture of sulphate i Glaseritc+KGl The salts are subjected to agitation with G00 kg. H20

374 kg. K 804 are obtained as product or The sulphate mother liquor together with the inspissated, l

carbonate mother liquor is used as initihlliquon T G00 32 25 ll i I 105 M'a'nufuctmje of 'magneszn'ni chlor de h [g(NH',)2(CO3)2+4aq 154 257 There are removed by drying at 100 73 kg. Nil -HM kg. (10 I I 10:; kg. H1O 154 l28 Dry residue 180 kg. lNlgCOi l27 'lhe MgCOa is mixed with 250 kg. NHJI and heated to 300 A 166 There are removed 21 kg. NlLCl, 73 kg. NH3, 94 kg. CO1 and 39kg. FLO 1 15 127 r Residue 203 kg. i\IgClg=produet 151 Sodium bicarbonate fl. 2 3M1 1 15 When calcining, 135 kg. 002 and 55 kg. 1120 are re1noved 0. .4 184 Residue 327 kg. NazOOa=product 142 185 NH; CO7

Balance of ammonia and carbonic acid Employed: kg. kg.

Glaserite separation 400' Double-carbonate separation 200 380 Bicarbonate. precipitation 100 460 i 700 s40. Obtained:

Eyaporating. after glaserite separation Drying Mg(NHi)2(COa)2+4 aq Manufacture of magnesium chloride. Liquor inspissation J. Manufacture oi s'oda Gonsum tion p r V.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is 1. A process for working up crude sylvinitic potash salts containing kieserite, consisting in hydrating the kieserite contained in crude sylvinitic potash salts, treating the said salts with an ammoniacal solution of ammonium chloride, removing the potassium sulphate containing sodium sulphate, treating the mother liquor with carbon dioxide for the purpose of precipitating magnesium ammonium carbonate, cooling the said mother liquor in order to remove a portion of the ammonium chloride contained therein and treating the remaining mother liquor with carbon dioxide for the purpose of precipitating sodium bicarbonate, as set forth.

2. A process as claimed in claim 1 and in which the said potassium sulphate containing sodium sulphate is treated with Water for the purpose of removing its content of sodium sulphate, and the resulting solution returned to the process, asset forth.

3. A,' process as claimed in claim 1 and in which the said magnesium ammonium carbonate is heated to a slight extent, ammonia and carbon dioxide being recovered for the process and magnesium carbonate obtained, as set forth.

4. A process as claimed in claim 1 and in which the said magnesium carbonate and ammonium chloride are mixed and heated for the purpose of recovering ammonia and carbon dioxide for the process and obtaining anhydrous magnesium chloride as product, as set forth.

5. A process as claimed in claim 1 and in which the said magnesium ammonium carbonate and ammonium chloride are separated together for the recovery of ammonia and carbon dioxide for the process, and thereupon heated together, anhydrous magnesium chloride being obtained, as set forth.

6. A process as claimed in claim 1 and in which the said magnesium ammonium carbonate and ammonium chloride are separated each individually for the recovery of ammonia and carbon dioxide, and heated in mix- 7 ture, anhydrous magnesium chloride being obtained, as set forth.

In testimony whereof we have signed our names to this specification.

THEODOR THORSSELL. AUGUST KRISTENSSON. 

